If you weren't already aware, it's entirely possible to load on a completely different operating system to your Chromebook, and recently Google even made it possible to load up Linux distros like Ubuntu through a virtual window on the Chromebook so you don't have to pop back and forth between the two OS platforms through a complete boot. Basically you could have Chrome OS continually running while Ubuntu ran in a window much like any other Chrome web app. Today Google's Fran§ois Beaufort took to Google+ to let Chromebook owners know that they're simplifying the process for loading on custom code to Chromebooks thanks to some new abilities to add debugging features when the Chromebook is in developer mode.
These new features offer up a handful of different and useful things for anyone interested in tinkering around with them, but they can only be accessed during the "out of the box" experience as debugging features lower system security. To get to the point where you can mess around with things if you've already been using your Chromebook for some time, you'll first have to enter into the Dev Channel on your Chromebook, powerwash your device, then click on the enable debugging features link that pops up.
The new debugging features include the ability to remove rootfs verification so you're able to modify OS files, enable SSH access to the device using the standard test keys so you can use tools such as cros flash, enable booting from USB so you can install an OS image from a USB drive, and set both the dev and and system root login password to a custom value so you can manually SSH into the device. If you're a developer, these new sets of tools should be of great use to you and your Chromebook of choice. There was no mention on whether or not these features will ever be available outside of the dev channel, but we wouldn't be surprised if Google and the Chromium team rolled them out for use by anyone and everyone who owns a Chromebook at some point in the future. On the original G+ post about these new features you can also find some useful links that can aid you in using the new debugging features.